I used straw, but yes, I made it two layers tall. I'm going to plant it this spring and see how it does. At the same time, I think I'll make another straw frame 1 layer deep around this one, leaving a couple of feet between the old frame and the new one. Then I'll fill that in with wood and a few layers of compost. When all is said and done, it
should just settle into a big mound.
We get about 33" of rain a year. I'm in WI, so with the cold weather, it hasn't really done much of anything since I built it. I would expect it to break down quite a bit this summer and incorporate the straw bales a big soil mound.
I'm not really worried about the compost. The city picks up all the leaves and grass clippings, etc., and just leaves them in a big pile that they turn with heavy machinery. You just back up and get a pick up load whenever you need it. They also have mountains of leaves. I had a friend sew some king size sheets into big bags, I'm going to bring a few bags of those home too, and start my own leaf mold pile.